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Honghsanosaurus
Hongshanosaurus (meaning "Red Hill lizard") is a genus of psittacosaurid ceratopsian dinosaur from the Early Cretaceous Period (about 125 million years ago) of eastern Asia. Although two skulls are the only fossil material described, comparisons with close relatives suggest it was a small, bipedal herbivore with a bony beak on the end of both upper and lower jaws. This is one of the many exceptionally well-preserved fossils to be recovered from the Yixian Formation of Liaoning, China. Discovery and species The generic name Hongshanosaurus is derived from the Mandarin Chinese words 紅 (hóng: "red") and 山 (shān: "hill"), as well as the Greek word sauros ("lizard") . This name refers to the ancient Hongshan culture of northeastern China, who lived in the same general area in which the fossil skull of Hongshanosaurus was found. The type and only named species, H. houi, honors Hou Lianhai, a professor at the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing, who curated the specimen. Genus and species were both named by Chinese paleontologists You Hailu, Xu Xing, and Wang Xiaolin in 2003. The holotype specimen of Hongshanosaurus, IVPP V12704, is a juvenile skull, completely preserved except for part of the right side and the tip of the upper jaw. This skull is slightly less than five centimeters (2 in.) long (You et al. 2003). A much larger adult skull was later described, specimen IVPP V12617, which is almost twenty centimeters (8 in.) long. It is very similar to skulls of the closely related Psittacosaurus, although several differences exist which serve to differentiate the two genera. Hongshanosaurus has a lower skull than any species of Psittacosaurus and the orbit (eye socket) is elliptical instead of round (You & Xu 2005; note that Sereno 2010 regarded the differences in proportion as due to crushing and compression of the Hongshanosaurus skullsSereno, Paul C. (2010). Taxonomy, cranial morphology, and relationships of parrot-beaked dinosaurs (Ceratopsia:Psittacosaurus). In: Ryan, Michael J., Chinnery-Allgeier, Brenda J. & Eberth, David A. (Eds.). New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium. Bloomington and Indianapolis: Indiana University Press. Pp. 21–58.). These skulls were recovered from the Yixian Formation of Liaoning, China, which is famous for the exceptional preservation of its fossils, including most of the known feathered dinosaurs. The age of this formation has been radiometrically dated to the early Aptian age of the Early Cretaceous, about 125 million years ago. Several specimens of Psittacosaurus have also been recovered from the Yixian, including one with a row of long bristles on the tail which may have had a display function in life. As Hongshanosaurus is known only from skull material, it is unknown whether it also had these bristles. Classification Hongshanosaurus was placed in the family Psittacosauridae when it was first described, but has not been included in any phylogenetic analysis since. The only other genus currently classified in this family is Psittacosaurus itself, although that genus includes up to a dozen individual species. Psittacosaurids are extremely basal ceratopsians. The more inclusive group Neoceratopsia is in fact defined to include all ceratopsians more derived than Psittacosauridae (You & Dodson 2004). Sereno (2010) regarded Hongshanosaurus as a junior synonym of Psittacosaurus, and potentially the same as P. lujiatunensis. He did not synonymize the two species because of difficulties with the holotype skull of H. houi, instead considering new combination P. houi a nomen dubium within Psittacosaurus. References *You H., Xu X. & Wang X. 2003. A new genus of Psittacosauridae (Dinosauria: Ornithopoda) and the origin and early evolution of marginocephalian dinosaurs. Acta Geologica Sinica (English edition) 77(1): 15–20. *You H. & Dodson, P. 2004. Basal Ceratopsia. In: Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.). The Dinosauria (2nd Edition). Berkeley: University of California Press. Pp. 478–493. *You H. & Xu X. 2005. An adult specimen of Hongshanosaurus houi (Dinosauria: Psittacosauridae) from the Lower Cretaceous of Western Liaoning Province, China. Acta Geologica Sinica (English edition) 79(2): 168-173 Category:Dinosaurs of Asia Category:Ceratopsians Category:Cretaceous dinosaurs